Axillary lymph node dissection plus radiotherapy may be an optimal strategy for patients with occult breast cancer

Background:Because of the rarity of occult breast cancer(OBC)and limited experience in OBC treatment,the optimal treatment strategy is unknown.This study aimed to compare the efficacy of axillary lymph node dissection(ALND)plus radiotherapy with that of mastectomy plus ALND in patients with OBC.Methods:Relevant clinical data between January 2004 and December 2015 were retrospectively collected from the Surveillance,Epidemiology,and End Results database.The clinical characteristics and prognoses of patients who underwent ALND plus radiotherapy or mastectomy plus ALND were compared before and after propensity score matching.Results:Overall,569 eligible patients with OBC were included in this study.Of these,247 patients underwent ALND plus radiotherapy and 322 underwent mastectomy plus ALND.The 5-year overall survival(OS)rates in the ALND plus radiotherapy group and the mastectomy plus ALND group were 89.2%and 80.6%,respectively;and the corresponding 5-year breast cancer-specific survival(BCSS)rates were 95.2%and 93.0%,respectively.After propensity score matching,the OS in the ALND plus radiotherapy group was significantly better than that in the mastectomy plus ALND group.In addition,further subgroup analyses revealed that ALND plus radiotherapy prolonged OS in the pN3 subgroup.Among patients receiving adjuvant chemotherapy,those who underwent ALND plus radiotherapy had better BCSS and OS than those who underwent mastectomy plus ALND.Conclusions:ALND plus radiotherapy could improve the OS of patients with OBC,especially those with pN3 disease and those receiving chemotherapy.ALND combined with radiotherapy is the optimal treatment strategy for patients with imaging-negative OBC.